A stent is a generally longitudinal tubular device formed of biocompatible material, preferably a metallic or a plastic material, which is useful in the treatment of stenosis, strictures or aneurysms in body vessels such as blood vessels. It is well known to employ a stent for the treatment of diseases of various body vessels. The device is implanted either as a "permanent stent" within the vessel to reinforce collapsing, partially occluded, weakened or abnormally dilated sections of the vessel or as a "temporary stent" for providing therapeutic energy treatment to the diseased vessels. Stents are typically employed after angioplasty of a blood vessel to prevent restenosis of the diseased vessel. Stents may be useful in other body vessels such as the urological tract and bile duct. The temporary stent is defined in this invention as a stent that is expandable inside a vessel and retractable thereafter from the vessel of a patient.
Stents generally include an open flexible configuration. The stent configuration allows the stent to be configured in a radially compressed state for intraluminal catheter insertion to an appropriate site. Once properly positioned adjacent the damaged vessel, the stent is radially expanded so as to support and reinforce the vessel. Radial expansion of the stent may be accomplished by an inflatable balloon attached to the catheter or the stent may be of the self-expanding type that will radially expand once deployed. One stent example is U.S. Pat. No. 4,733,665 to Palmaz, which is incorporated by reference herein,
An expanded PTFE (ePTFE) vascular graft is well known to have a substantially non-thrombogenic fluorinated surface. An ePTFE patch is also used for repairing the ruptured blood vessel wall. An ePTFE graft and its process of making are well known to one who is skilled in the art. One ePTFE example is U.S. Pat. No. 3,953,566, which teaching is incorporated herein by reference.
U.S. Pat. No. 5,810,870 to Myers et al. discloses a stent covered by an ePTFE to take the advantage of the substantially non-thrombogenic properties of a fluorinated surface, wherein the ePTFE cover exhibits suitable expansion capabilities so as to enable the cover to expand upon expansion of the underlying stent. The ePTFE covered stent exposes the fluorinated ePTFE surface, not the stent surface, to the underlying tissue or the flowing blood stream. Occasionally, the ePTFE cover might shift itself from its associated stent because the ePTFE cover is loosely covering the stent. This misalignment phenomenon of an ePTFE cover on a stent becomes a clinical problem when the stent is non-retractably deployed because the ePTFE cover does not firmly adhere to the stent structure. Said ePTFE covered stent blocks the openness of the stent and does not allow blood to continuously provide nutrient to the tissue behind the implanted stent. Tissue necrosis might occur due to inadequate perfusion, especially for a long ePTFE-covered stent.
U.S. Pat. No. 5,824,046 to Smith et al. also teaches the advantage of the substantially non-thrombogenic surface property by covering the stent with an unsintered PTFE. The fluorinated surface of the covered stent by covering with an unsintered PTFE is biocompatible; however, the unsintered PTFE layer or sheet only loosely covers the stent structure and might shift from its intended position onto a stent. The covered stent by an unsintered PTFE still does not allow blood to continuously supply nutrient to the underlying tissue behind the stent. This might cause cells necrosis and result in vessel re-stenosis.
Therefore, there is an urgent clinical need to provide a surface fluorinated stent or a stent having its surface coated by fluorine-containing material while still preserve the openness of the stent configuration, such as a coil stent, a mesh stent, a scaffold stent, a sleeve stent, a porous stent, or a permeable stent. Preferably, the stent material surface is coated or adhered by fluorine, fluoride, or fluorine-containing material while the stent open surface structure is open for blood perfusion to the tissue of vessel walls.
U.S. Pat No. 4,632,842 to Karwoski et al., U.S. Pat. No. 4,718,907 to Karwoski et al., and U.S. Pat. No. 5,246,451 to Trescony et al. disclose one fluorine-containing coating technique for coating fluorine, fluoride, or fluorine-containing compound onto the surface of a substrate to have a very low surface energy and to be essentially non-thrombogenic. However, none of the above-referred patents teaches coating fluorine, fluoride, or fluorine-containing compounds onto a stent that has a very small stent material surface to open surface ratio. Other preferred techniques of depositing fluorine-containing material onto a stent include dipping, dip coating, pasting (or paste coating), and/or sintering processes.
Furthermore, RF therapeutic protocol has been proven to be highly effective when used by electrophysiologists for the treatment of tachycardia; by neurosurgeons for the treatment of Parkinson's disease; and by neurosurgeons and anesthetists for other RF procedures such as Gasserian ganglionectomy for trigeminal neuralgia and percutaneous cervical cordotomy for intractable pains. Radiofrequency treatment, which exposes a patient to minimal side effects and risks, is generally performed after first locating the tissue sites for treatment. Radiofrequency energy, when coupled with a temperature control mechanism, can be supplied precisely to the apparatus-to-tissues contact site to obtain the desired temperature for treating a tissue.
A stent deployed within a vessel, such as a coronary stent, has excellent metal-to-tissue contact surface. It becomes an ideal medium for applying thermal energy to the tissue needed for treatment or modulation. RF energy can be applied to a surface fluorinated stent to render the stent less prone to re-stenosis. Therefore, there is a need for an improved intraluminal medical device having a fluorinated surface and the capability to contact the inner walls of a tubular vessel using the radiofrequency energy to effectively treat and support/reinforce an enlarged artery or other tissues.